1. Field of the Invention
This invention relates to lighting systems, and more particularly, to a thin aspect forward lighting system with cutoff.
2. Description of the Related Art
At present, there are two large families of headlights. A first family, those of headlights herein called “of the parabolic type”, comprises headlights whose beam is mainly generated by a source of small dimensions mounted in a mirror which projects the rays onto the road in order to form the desired beam. The window of the headlight is involved, if necessary, by being fitted with prisms, striations, and the like, in order to model the beam, and in particular, in order to spread it widthwise. In this case, this family includes the headlights called “free-surface” or else “Surface Complexe” (registered trademark) headlights, having the ability of directly generating a beam delimited by a desired upper cut-off line.
These headlights have the properties of being able to generate beams of excellent quality in terms of light distribution, and of being, in general, not very deep. However, in order to generate a sufficiently intense beam, it is necessary that their mirror or reflector recovers a significant proportion of the light flux emitted by the lamp.
A first approach to doing this consists in using a very small initial focal length, especially in order to obtain a mirror which is very close around the source and of small size widthwise. However, in this case, because of the large size of the images of the source generated by the mirror, the beam has in general an excessive thickness, and is in any case difficult to control.
A second approach to recovering the light flux while obtaining a thinner beam consists, on the contrary, in increasing the initial focal length, but in this case the mirror must have relatively large dimensions transversely to the optical axis, which is counter to the objective of a compact headlight.
A second family is that of headlights “of the elliptical type”. Such headlights are characterized by a lamp mounted in a mirror which generates, with the reflected rays, a concentrated spot (typically, the source is at the first focus of a mirror in the shape of an ellipsoid of revolution and the spot is formed at the second focus of the mirror), and this spot is projected onto the road by a convergent lens, usually a plano-convex lens. If the beam has to comprise a cut-off line, the latter is produced by partly occluding the light spot where it is formed.
This second family of headlights has the advantage of being able to recover a significant proportion of the light flux emitted by the source, while having small dimensions transversely to the optical axis. On the other hand, the photometry of the beam may prove to be difficult to model, since by nature no correcting element of the prism or striated type can in general correct the light downstream of the lens; furthermore, these headlights have a large size depthwise.
Furthermore, in practice, these two families of headlights have very different external appearances.
Thus, the headlights of the parabolic type have a window with a relatively large width (while throughout the years, for reasons of style and aerodynamics, their height has gradually reduced). This window is striated or, in more recent styles, virtually smooth such that, when the headlight is extinguished, the mirror and various types of trims are observed perfectly on the inside.
In contrast, a headlight of the elliptical type, when it is extinguished, in general reveals only the outer convex face of the lens, which is often surrounded with a suitable trim, through a smooth window.
Nowadays, there are ever more demanding requests from designers relating to the appearance of illuminating headlights for vehicles.
Thus certain style “trends” favor headlights of parabolic type, or of elliptical type, or even a combination or use of both types.
Moreover, on a more technical level, there is a strong demand for headlights having a size which is moderate not only transversely to the optical axis, but also depthwise, that is to say along the optical axis, which, in principle, neither of the two families of headlights mentioned above is able to obtain without making concessions in terms of quality of illumination.
One solution of the prior art is found in U.S. Pat. Nos. 7,980,742; 7,168,836 and 6,811,289. The lens width is wider than requested by a customer and requires a diverging lens solution. The formation of a kink or elbow in the beam pattern is not demonstrated.
The following are some additional problems with prior art designs:
Conventional lens systems cannot be adapted to customer styling for thin lens elements.
Conventional lens systems (imaging/projection lens systems) have color dispersion that may be objectionable when driving or must be managed in the design using more complex lenses.
Conventional lens systems require more complex molding.
The invention herein overcomes one or more of the problems of the prior art.